The present invention relates to joints for folding ladders, furniture and the like, and more particularly, to a joint mechanism for pivotal connection of ladder or furniture sections which permits the associated sections to be freely folded or unfolded, positionally adjusted, and locked in a predetermined angular position.
Known joints for folding ladders which are pivotable, angularly adjustable, and lockable are disclosed, for example, in West Germany Pat. No. 2052584 to Hoffman. This type of joint comprises a first joint member and a second joint member which are pivotally connected together. The first joint member has at its front end two spaced-apart, symmetrically arranged disks between which there are provided a spring-loaded locking element and an operating lever. The rear end of the first joint member is a tubular portion adapted to fit around one end of one ladder section. The second joint member has at its front end a hollow, flat locking disk formed of a pair of circular shell halves encasing a spring-biased sector-shaped ratchet, and at its rear end a tubular portion adapted to be connected to the other ladder section. Distributed about the circumferential edge of the locking disk are notches engageable with the locking element of the first joint member for selectively locking the ladder in one of a series of predetermined positions. The locking disk of the second joint member is sandwiched between the two disks of the second joint member, and a joint pin is provided to secure these disks together in such a manner that the first and second joint members can pivot relative to each other about the pin. In the joint of such construction when the operating lever is operated to cause disengagement of the locking element from its associated notch, the sector-shaped ratchet provided in the second joint member will close that notch to prevent return of the locking element into same while uncovering the notch at the desired position for the ratchet to engage. That is, upon shifting of the lockable positions or folding and unfolding of the ladder sections, the ratchet acts to permit or hinder engagement of the locking element in the respective notches by uncovering or closing the appropriate notch. However, since the ratchet is formed with peripheral teeth each of which projects outwardly of the joint through a notch, the outwardly projecting teeth tend to cause injuries such as a scratch to the user or to become caught on clothing. In addition, such teeth may result in malfunction of the joint due to susceptibility to damage when encountering impacts or external forces. Moreover, since the locking disk of the second joint member is constructed of two symmetrically superposed shell halves of sheet metal, it will be rather cumbersome to assemble the ratchet and the spring for biasing the ratcher within the locking disk during the manufacturing process.
Accordingly, the present invention overcomes the abovementioned disadvantages by providing an improved joint mechanism which insures safety in use while being easy to operate.
It is an object of the invention to provide a joint mechanism which has no unduly protruded parts which may result in injuries to the user or become caught on clothing.
It is another object of the invention to provide a joint mechanism which is easy to manufacture and assemble and free from malfunction in use.
It is still another object of the invention to provide a joint mechanism which employs a clawed control means entirely received within the joint mechanism and including a plurality of resilient arms in place of the conventional sector-shaped ratchet, and an operating lever constructed in two pivotally related sections in place of the conventional one-piece operating lever, the operating lever cooperating with the clawed control means to control movement of a pawl between its locking and releasing positions so as to adjust and lock the joint mechanism in one of a series of predetermined positions.